RE: Two-step NFC OOB pairing and immediate pairing

WoutWG — Tue, 05 Mar 2024 14:06:20 GMT

Hi Kenneth,

Thank you for the feedback. I was able to transfer the 'remote' bt_le_oob and to use that for pairing when accessing a characteristic with the BT_GATT_PERM_READ_LESC permission. I can indeed also implement a timeout to disconnect when the security level is not raised within a certain amount of time.

I was just wondering how it works with the Bluetooth: NFC Pairing sample, since there the phone automatically asks to pair with the device when scanning the tag, seemingly before there is any interaction with any characteristic or even before a connection is set up. But that's mostly informational and not really a requirement, since I got everything working now, so I'll verify your answer.

RE: Two-step NFC OOB pairing and immediate pairing

Kenneth — Thu, 29 Feb 2024 14:02:22 GMT

Hello,

This is kind of a big topic of questions here, but here are some pointers I have.

So NFC here is just used to transfer some data between the two peers, and you are using the phone as a way to transport that data. I do believe that should work, likely you can just the generic NFC example, and replace the "Hello World" with the OOB data and possible the name, address or irk of the peer (just to make sure the correct peer connect in the first place):
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/nfc/record_text/README.html

In terms of how to use the OOB data on the peer, I suggest to for instance look at the auth_oob_data_request() in main.c for peripheral_keyboard and replace app_nfc_oob_data_get() with the 128-bit key you want to use. Similar on central you need to add the .oob_data_request callback in conn_auth_callbacks to handle such event.

You are right that by default it will connect using no security, and to ensure that it's not "stuck" in a connection with an invalid peer, I suggest to add some timeout that for instance after 1-2seconds the peer will disconnect if it has not achieved the desired security level.

Kenneth